1. Field of the Invention
The present invention relates to a sealing device relating to a seal technology, and more particularly to a reciprocating sealing device. The sealing device according to the present invention is used, for example, in a damper mechanism for a motor vehicle, or used in the other damper mechanisms.
2. Description of the Conventional Art
A damper mechanism 51 shown in FIG. 6 has been conventionally known, and a sealing device 61 is embedded in the damper mechanism 51 for sealing an oil O which is sealed in an inner portion.
The shown damper mechanism 51 is structured by combining a damper shaft 52 which is provided in a leading end with a piston 53 having an orifice 54, and a damper case 55 which is elastically supported by a spring means 56, and a sealing device 61 is embedded between the damper shaft 52 and the damper case 55 for sealing the oil O sealed in an inner portion of the damper case 55. Further, a seal 71 constructed by an O-ring or a gasket is mounted separately at a split position of the damper case 55 so as to seal the split position.
The sealing device 61 embedded between the damper shaft 52 and the damper case 55 is provided with a packing 62 which is mounted to an annular mounting groove 57 arranged in an outer peripheral surface of the damper shaft 52, and the packing 62 is integrally provided with an annular base part 63, a stationary side lip 64 which comes into close contact with a groove bottom surface of the mounting groove 57, and a sliding side lip 65 which slidably comes into close contact with an inner peripheral surface of a tubular portion of the damper case 55, as shown in FIG. 7
However, the following problems are pointed out in the prior art mentioned above.
(1) A volume of the oil is going to be small at a collapsing margin of the seal 71 by the damper case 55 at the oil sealing time (at the damper assembling time, however, since the oil is an incompressible fluid, the volume of the oil is absorbed by deformation of the packing 62.
(2) The volume of the oil which can not be absorbed by the deformation of the packing 62 causes an increase of an internal pressure.
(3) In the structure of the packing 62, an annular base part 63 is formed such that a cross sectional shape of a heel part 63a is an angled end, and is formed such that the annular base part 63 protrudes to the damper case 55 (an outer peripheral side, a left side in the drawing) from an extension 65c of an outer peripheral surface 65b of the sliding side lip 65 in a free state.
(4) According to the packing 62 having the structure mentioned above, the packing 62 slides in a full-surface contact state on the basis of the increase of the internal pressure. Here, the full-surface contact means that the packing 62 comes into contact with the damper case 55 over a whole surface between a lip end 65a of the sliding side lip 65 and the heel part 63a of the annular base part 63. Further, the internal pressure further increases on the basis of a viscous resistance of the oil by the reciprocating motion.
(5) According to the phenomena and structures (1) to (4) mentioned above, a large amount of oil leakage may be generated in the case that a high-frequency oscillation is input and a high-viscosity oil is used.
Further, as a prior art in relation to the present invention, there is the invention disclosed in Japanese Unexamined Patent Publication No. 2002-122241. The prior invention relates to “a packing for fluid pressure having an annular seal groove part which receives fluid pressure, an annular sliding side lip which is pressed to a sliding member by the fluid pressure, an annular heel part which faces to an opening end side of an attaching groove, an annular shoulder part which faces to a corner portion side of the attaching groove, and an annular fixed side lip which is pressed to a bottom surface of the attaching groove by the fluid pressure, wherein the packing for fluid pressure has an annular first inclined surface which is inclined from a leading end of the sliding side lip to the heel part in a free state in which the fluid pressure is not applied, so as to be away from the sliding member little by little, and the heel part is continuously curved from the first inclined surface”.
Accordingly, differences between the prior invention and the present invention are as follows.
(a) Since the prior invention starts deforming from the lip, the prior invention is disadvantageous to maintain a wedge shape. On the contrary, the present invention has a collapsing margin of the back ring, the lip shape can be maintained even after absorbing the initial internal pressure.
(b) Since the present invention is easily deformed only in the sliding side lip by the back ring, the deformation of the stationary side lip is hard to be generated, and stability of the seal is improved.
(c) Since the volume of the non-sealed area is increased by the back ring in the present invention, an allowable amount of the volume change is increased. Therefore, it is possible to stand against the increase of the internal pressure (the increase of the volume) at the using time.